As is known, many portable electronic apparatuses comprise mobile mechanical parts that must be protected from impact because they can easily get damaged. For example, portable computers or laptops are equipped with hard disks provided with extremely delicate read and write heads, which, in the case of impact, can break or damage the magnetic surfaces where the data are stored.
In order to limit the damage due to accidental impact, in particular following upon a fall, it has been proposed to use protection devices based upon inertial sensors, which detect a critical condition of motion and enable the electronic apparatus to be brought in a timely way into a safety configuration. For example, a free-fall condition is promptly recognized by the inertial sensor because the effect of the gravitational force normally detected is substantially zero (situation of zero gravity). In the case of the hard disk of a portable computer, the heads are immediately parked in a safety area, reducing the risk of damage.
However, there are common but non-dangerous situations in which the inertial sensor can detect the absence of gravity or other anomalous conditions of motion for a short period of time. These situations, which can arise when the user is walking or when a portable computer is on the user's lap, should preferably not correspond to emergency measures. To discriminate non-dangerous events, known protection devices are provided with circuit blocks for checking whether the critical conditions of motion are protracted for at least for a threshold time interval. The emergency measures are hence activated only with the consent of said circuit blocks, after a time considered sufficiently long has elapsed. Otherwise, the count of the duration of the time interval is reset, and the electronic apparatus incorporating the protection device remains in its normal operating configuration.
In some cases, however, a temporary interruption of the critical conditions of motion can have drastic consequences. For example, if a user makes an unsuccessful attempt to stop the fall of an electronic apparatus that has slipped out of his grip, only managing to slow it down, it can happen that the emergency measures are not activated. The motion of the electronic apparatus could thus be broken down into various steps of free fall, which are all too short and of a duration shorter than the threshold time interval that enables recognition of the condition of danger. The electronic apparatus hence remains in the normal operating configuration, and the impact that ensues due to the fall can cause more or less serious damage to the parts that are not protected.